title: Soft collective fluctuations governing hydrophobic association.
abstract: The interaction between two associating hydrophobic particles has traditionally been explained in terms of the release of entropically frustrated hydration shell water molecules. However, this picture cannot account for the kinetics of hydrophobic association and is therefore not capable of providing a microscopic description of the hydrophobic interaction (HI). Here, Monte Carlo simulations of a pair of molecular-scale apolar solutes in aqueous solution reveal the critical role of collective fluctuations in the hydrogen bond (HB) network for the microscopic picture of the HI. The main contribution to the HI is the relaxation of solute-water translational correlations. The existence of a heat capacity maximum at the desolvation barrier is shown to arise from softening of non-HB water fluctuations and the relaxation of many-body correlations in the labile HB network. The microscopic event governing the kinetics of hydrophobic association has turned out to be a relatively large critical collective fluctuation in hydration water displacing a substantial fraction of HB clusters from the inner to the outer region of the first hydration shell.
authors.affiliation: National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia and Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany.
authors.forename: Aljaž
authors.initials: A
authors.lastname: Godec
authors.forename: Jeremy C
authors.initials: JC
authors.lastname: Smith
authors.forename: Franci
authors.initials: F
authors.lastname: Merzel
mesh_terms: D003198:Computer Simulation; D019277:Entropy; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D009010:Monte Carlo Method; D012996:Solutions / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D012996:Solutions; D014867:Water